In the art of burning fuels in air for any purpose, and regardless of the manner in which the fuel is burned, there is oxidation of the nitrogen, which is a part of the air used as a source of oxygen for combustion of the fuel.
Oxidation of nitrogen, which is an endothermal reaction results in the presence of NOx, as either or both of, NO and NO.sub.2. Oxides of nitrogen, through atmospheric reaction, produce "smog", and because of this the NOx content of gases discharged to the atmosphere is severely limited by various state and federal agencies.
Widely reported researches have shown that if water, or water vapor, is added to the air for combustion, or if water is added to the combustion zone in any convenient manner (such as water injection to internal combustion engines in aircraft) certain beneficial effects are noted, such as accelerated burning of fuel, lowering of ignition temperature, greater power generation and reduction of NOx emission as has been discovered in later work. However, the reduction in Nox emission is far from adequate for compliance with existing regulations. In the prior art it has been well known to inject steam into the flame zone where combustion is in progress to improve the overall operation of fuel burning. However, the premixture of water with fuel prior to combustion reaction has neither been examined nor reported in prior research as far as is known in point of reduced NOx emission.
This invention lies in the field of combustion of fuels. More particularly, it concerns combustion of fuels in a way to reduce the NOx emissions to the atmosphere. Still more particularly it concerns methods of adding water or water vapor to fuel in sufficient quantity, prior to entering the combustion zone, so as to facilitate combustion and to reduce the NOx emissions down to the level required by regulatory agencies. While the method can be applied to all fluid fuels, it has greatest advantage with gaseous fuels.